You’ll spend about 4,000 hours of your adult life showering -- possibly more time than you spend reading, exercising or watching TV -- but chances are, you’ve been doing it wrong.If you take a morning shower, you probably think it energizes you for the day, but it can actually have the opposite effect.In fact, a hot shower or bath is what many doctors recommend for people who have trouble falling asleep -- to help them fall asleep. The reason: Emerging from a hot shower into cooler air brings a sudden decrease in body temperature, leading to a tranquil state of mind. This is helpful when you’re looking to fall asleep but not what you need before you start your day.If your goal is to wake up in your morning shower, then you need to make a 90-second tweak.Related: Productive Ways to Jumpstart Your DayThe secret lies in the contrast. Here’s how to do it:Once you’ve finished your normal cleaning ritual, crank the nozzle as cold as it goes, and stand under the water for about 30 seconds. Feel free to gasp or scream if it helps (some say it does).After 30 seconds, turn the water up as hot as you can stand for another 30 seconds. This opens up the capillaries, increases blood flow and provides an all-around sense of stimulation.Finally, cap it off with one more cycle of icy cold. Always end on cold.You might be asking, “Why would I put myself through such discomfort first thing in the morning?” Because it works.Hot and cold hydrotherapy has been used for thousands of years. In Finland, the sauna isn’t a luxury; it’s a necessity. The country is home to 2 million saunas (for a population of 5 million) with 99 percent of Finns enjoying the stress-relieving benefits of the sauna at least once a week.Related: 18 Unusual Habits That Boost Your Energy More Than CoffeeI trust the Finns and scientific research provides further confirmation. Studies have shown that it provides a full-body tune-up, including:Reducedstress: In a study on free radicals, 10 healthy subjects swam regularly in ice-cold water and showed adaptation to oxidative stress and hardening (an increased tolerance to stress). When building a business, combating stress is crucial for achieving clarity of mind.A stronger immune system: Another study found that taking daily cold showers increases the number of disease-fighting white blood cells. In an attempt to warm up, the body speeds up its metabolic rate and activates the immune system, releasing more white blood cells.Improved blood circulation: When exposed to cold water, our arteries and veins constrict. This temporary tightening allows blood to flow at a higher pressure, which is great for cardiovascular health.Increased ability to burn fat: Research shows that cold-induced glucose uptake results in the creation of brown fat cells, which create warmth, burn energy and keep you slim.Aid in battling depression: A 2008 study found that adapted cold showers stimulate the sympathetic nervous system and increase beta-endorphin levels in the blood. They send a high level of electrical impulses from peripheral nerve endings to the brain, which could produce an anti-depressant effect.While trying out this new routine, youshould fully expect discomfort but be equally prepared to start your day feeling more refreshed than ever before.